As an engine coolant circuit circulating coolant to cool an engine, for example, Patent Document 1 discloses an engine coolant circuit in which the coolant flows out of the engine and discharges waste heat thereof in a radiator before returning to the engine.
To increase the amount (capacitance) of the coolant in such an engine coolant circuit, typically, a coolant tube is increased in diameter or a component of the engine coolant circuit, such as a thermostatic switching valve, is increased in size.